The idea behind adding naloxone to opioids is to make them less attractive to inject.
Basically, naloxone's oral bioavailability is like 1%, while IV bioavailability is by definition 100%. So if you eat your pills as intended, virtually none of the naloxone will make it past the liver, and the only thing you'll feel is the opioid agonist. If you inject it, you'll suffer precipitated withdrawal because the naloxone's antagonism will overpower the active opioid's agonism.
While the practice does not seem to be commonplace in the US (with the exception of the blockbuster drug suboxone), in Germany the popular opioid tilidine is usually sold as a combination drug with naloxone ("Valoron N") to decrease abuse. Ditto for oxycodone, which is available in a naloxone combo called "Targin". I believe in North America, it is mostly done with pentazocine ("Talwin NX").
In all these cases, the combination makes perfect sense, because the naloxone can easily kick the tilidine/oxy/pentazocine off the receptors. With suboxone, the issue is a little more iffy - buprenorphine itself binds to the receptors just as strongly as naloxone, so the naloxone can mayyybe blunt the initial euphoria of a bupe injection to some extent by competing for the same receptors, but not send you into withdrawal. That's why a lot of people are saying that the primary reason for adding the naloxone was less about deterring people from injecting it, and mostly about having a patentable "new" drug.
This was amazing info. Thank you. I do have some questions though. If I understand you correctly, the reason so many of the more educated people in here seem to believe that the naloxone component is virtually inconsequential is because the oral bioavailability (post first pass obviously) is virtually nill ( 1% )
1 - Fine, makes sense if you're taking naloxone as a pill. But suboxone is administered as an intra-mucosal strip that dissolves. Or a sublingual version called Zubzolve (sp?) which is much better because it comes in like 1mg (possibly smaller) increments. Either version skips first pass. So what's the bioavailability of naloxone then? And what about the buprenorphine?
2 - And why in God's name would they combine an antagonist and a full agonist Targon, Valoron)? Is there a reason beyond preventing injection? Do you happen to know how much naloxone they put in each?
3 - You mentioned the naloxone perhaps blunting the initial euphoria of the bupe administration. For the life of me I've never detected even the slightest hint of euphoria on it. Not even a little mood elevation...or the initial energy boost like you get with, say, methadone. Nothing! I also believe that's at least 75% of the reason it's more effective than methadone at achieving long term sobriety. I literally dropped from 24mg of suboxone to 4mg in under a month. I dropped from 24mg to 16mg overnight, a weak later, dropped another 8mg, and roughly 2 weeks later I dropped to 4mg. Those are big drops that are usually not recommended but I gotta tell you, I literally felt nothing. No difference. When I got down to 4mg there were literally days where I'd simply forget to take it. Do a lot of people claim they get a sense of euphoria from suboxone?
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